Method for sending status information in mobile telecommunications system and receiver of mobile telecommunications

ABSTRACT

Disclosed is a method of sending status information (STATUS PDU) in which a receiving side reports a data received state to a transmitting side in a mobile telecommunication system. A receiving side RLC entity considers an available radio resource to construct a status PDU fit to the size of the radio resource and then sends the constructed status PDU to a transmitting side RLC entity, thereby avoiding a deadlock situation of RLC protocols.

The present application claims the priority benefits of U.S. ProvisionalApplication No. 61/025,267 filed on Jan. 31, 2008 and Korean PatentApplication No. 10-2009-0006356 filed on Jan. 23, 2009 in Republic ofKorea. The entire contents of these applications are herein fullyincorporated by reference.

TECHNICAL FIELD

The present invention relates to a radio protocol in a mobilecommunication system, and more particularly, a method for sending statusinformation (STATUS PDU) in which a receiving side reports a datareceived state to a transmitting side, in an evolved universal mobiletelecommunications system (E-UMTS) evolved from the UMTS.

BACKGROUND ART

FIG. 1 is a network architecture of a long term evolution (LTE) systemwhich is the related art mobile communication system has evolved fromthe existent UMTS system and a basic standardization therefor isundergoing in 3GPP.

The LTE network may be divided into evolved UMTS terrestrial radioaccess network (E-UTRAN) and core network (CN). The E-UTRAN includes aterminal (User Equipment; UE), a base station (Evolved Node B; eNB), anaccess gateway (aGW) located at the end of the network to be connectedto an external network. The aGW may be divided into a portion ofhandling a user traffic and a portion of processing a control traffic.Here, a new interface may be used for the communication between the aGWfor processing the user traffic and the aGW for processing the controltraffic. One or more cells may exist in one eNB. An interface fortransmission of the user traffic or control traffic may be used betweeneNBs. The CN may include an aGW, a node for a user registration of otherUEs and the like. An interface may be used to identify the E-UTRAN andCN.

FIG. 2 is an architecture of a radio interface protocol control planebetween a terminal and an E-UTRAN based upon the 3GPP radio accessnetwork standard, and FIG. 3 is an architecture of a radio interfaceprotocol user plane between a terminal and an E-UTRAN based upon the3GPP radio access network standard.

Hereinafter, the architecture of radio interface protocols between theterminal and the E-UTRAN will be described with reference to FIGS. 2 and3.

The radio interface protocol has horizontal layers comprising a physicallayer, a data link layer and a network layer, and has vertical planescomprising a user plane for transmitting data information and a controlplane for transmitting a control signaling. The protocol layers can bedivided into a first layer (L1), a second layer (L2) and a third layer(L3) based on three lower layers of an Open System Interconnection (OSI)standard model widely known in communications systems. Such radiointerface protocols may exist as a pair between the terminal and theE-UTRAN, to manage data transmissions over interfaces.

Hereinafter, each layer in the radio protocol control plane in FIG. 2and the radio protocol user plane in FIG. 3 will be described.

A first layer, as a physical (PHY) layer, provides an informationtransfer service to an upper layer using a physical channel. Thephysical layer is connected to its upper layer, called a Medium AccessControl (MAC) layer, via a transport channel. The MAC layer and thephysical layer exchange data via the transport channel. Here, thetransport channels may be divided into a dedicated transport channel anda common transport channel depending on whether the transport channel isshared. Data is transferred via a physical channel between differentphysical layers, namely, between the physical layer of a transmittingside and the physical layer of a receiving side.

Various layers exist in the second layer. First, a medium access control(MAC) layer serves to map different logical channels to differenttransport channels, and also performs a logical channel multiplexing formapping several logical channels to one transport channel. The MAC layeris connected to an upper radio link control (RLC) layer via a logicalchannel. Logical channels are divided according to a type of informationto be transmitted into a control channel for transmitting control planeinformation and a traffic channel for transmitting user planeinformation.

The RLC layer of the second layer manages segmentation and concatenationof data received from an upper layer to appropriately adjust a data sizesuch that a lower layer can send data over an interface. Also, the RLClayer provides three operation modes, including a transparent mode (TM),an un-acknowledged mode (UM) and an acknowledged mode (AM), so as toguarantee various quality of service (QoS) requirements of each radiobearer (RB). In particular, the RLC layer operating in the AM mode(hereinafter, referred to as AM RLC layer) performs a retransmissionusing an automatic repeat and request (ARQ) function for a reliable datatransmission.

A packet data convergence protocol (PDCP) layer located at the secondlayer is used to efficiently transmit IP packets, such as IPv4 or IPv6,on a radio interface with a relatively narrow bandwidth. For thispurpose, the PDCP layer reduces the size of an IP packet header which isrelatively great in size and includes unnecessary control information,namely, performs a function called header compression. Accordingly, onlynecessary information can be included in the header part of data fortransmission, so as to increase a transmission efficiency of a radiointerface.

A radio resource control (RRC) layer located at the lowermost portion ofthe third layer is only defined in the control plane. The RRC layercontrols logical channels, transport channels and physical channels inrelation to configuration, re-configuration and release of Radio Bearers(RBs). Here, the RB denotes a logical path that the L2 layer providesfor data transmission between the terminal and the UTRAN. In general,the establishment of the RB refers to stipulating the characteristics ofprotocol layer and channel required for providing a specific service,and setting the respective detailed parameters and operation methods.The RBs are divided into a signaling RB (SRB) and a data RB (DRB). TheSRB is used as a path for transmission of RRC messages in the C-plane,while the DRB is used as a path for transmissions of user data in theU-plane.

Hereinafter, the RLC layer will be described in more detail. The RLClayer provides three modes, such as the TM, UM and AM, as mentionedabove. The RLC layer rarely performs a function in the TM, and thus UMand AM will only be described herein. The UM RLC adds a protocol dataunit (PDU) header including a sequence number (SN) to each PDU fortransmission, such that a receiving side can be known as to which PDUhas been lost during transmission. Due to such function, the UM RLCmanages, in the user plane, the transmission of multimedia data or thetransmission of real-time packet data, such as voice (e.g., VoIP) orstreaming in a packet service domain (hereinafter, referred to as a PSdomain), while managing, in the control plane, the transmission of anRRC message, which does not need a reception acknowledgement, among RRCmessages sent to a specific terminal or specific terminal group within acell.

Similarly, the AM RLC constructs a PDU by adding a PDU header includingan SN upon the construction of PDU. Unlike the UM RLC, a receiving sideacknowledges a PDU sent by a transmitting side. The receiving sideacknowledges in order to request a retransmission of unsuccessfullyreceived PDU from the transmitting side. Such retransmission function isthe most important characteristic of the AM RLC. Thus, the AM RLC aimsto guarantee an error-free data transmission via the retransmission.Under the purpose, the AM RLC usually manages a non-real-time packetdata transmission, such as TCP/IP of PS domain, in the user plane, whilemanaging a transmission of RRC message, which requires a receptionacknowledgement, among RRC messages transmitted to a specific terminalwithin a cell in the control plane.

From the perspective of direction, the UM RLC is used for auni-directional communication, while the AM RLC is used for abi-directional communication due to a feedback from a receiving side.From the structural perspective, there is a difference, namely, the UMRLC is configured such that one RLC entity performs transmission orreception while the AM RLC is configured such that both transmittingside and receiving side exist in one RLC entity. The complicatedconfiguration of the AM RLC is due to the retransmission. The AM RLCincludes a retransmission buffer for managing the retransmission, inaddition to a transmission/reception buffer. Also, the AM RLC performsvarious functions, such as using transmitting and receiving windows fora flow control, polling for a transmitting side to request statusinformation from a receiving side of an RLC entity, sending a statusreport for a receiving side to report its buffer state to a transmittingside of a peer RLC entity, constructing a status PDU for deliveringstatus information, and the like. The AM RLC also needs various protocolparameters, such as status variables and a timer, in order to supportthe functions. A PDU, such as status report or status PDU, which is usedfor controlling the data transmission in the AM RLC, is referred to as‘Control PDU’, and a PDU used for transferring user data is referred toas ‘Data PDU’.

An RLC data PDU in the AM RLC may be divided into AMD PDU and AMD PDUsegment, in detail. The AMD PDU segment has part of data included in theAMD PDU. In the LTE system, a maximum size of a data block is changeableevery time a terminal sends the data block. Hence, after a transmittingside AM RLC entity constructs a 200-byte AMD PDU at a specific time andtransmits the constructed AMD PDU, when the transmitting side AM RLCreceives NACK from a receiving side AM RLC and thereby tries toretransmit the AMD PDU, if a maximum size of data block to be actuallytransmittable is 100 bytes, the same AMD PDU cannot be sent as it is. Inthis case, the AMD PDU segment is used. The AMD PDU segment denotes thatthe corresponding AMD PDU is segmented into smaller units. During theprocedure, the transmitting side AM RLC entity divides the AMD PDU intothe AMD PDU segments and transmits the AMD PDU segments over severaltransmission time intervals. The receiving side AM RLC entity thenrestores the AMD PDU from the received AMD PDU segments.

If there is unsuccessfully (incompletely or incorrectly) received data,the receiving side AM RLC requests a retransmission of such data fromthe transmitting side AM RLC, which is referred to as ‘status report’.The status report is sent by using STATUS PDU, which is one of controlPDUs.

DISCLOSURE Technical Solution

In the related art, when the status report is triggered, the receivingside AM RLC includes all information related to AMD PDUs, which fallwithin the range of VR(R) (e.g., a start point of a transmitting window)to VR(MS) (e.g., an end point of the transmitting window), in a STATUSPDU for transmission. However, if the size of radio resource to send theSTATUS PDU is smaller than the STATUS PDU, the constructed STATUS PDUcannot be sent. Actually, a radio resource allocation for a specificlogical channel is managed by a MAC layer. However, the MAC layer doesnot know the condition of the RLC. Accordingly, the MAC layer mayallocate radio resources less than being required for the transmissionof the RLC STATUS PDU. The related art does not concern about thesituation. As a result, when such situation occurs, the RLC STATUS PDUcannot be sent, thereby coming to a deadlock situation.

Therefore, an object of the present invention is to prevent an RLCprotocol from being in a deadlock situation, by allowing a transmissionof a STATUS PDU even when the size of an available radio resource issmaller than the STATUS PDU, in case where a receiving side RLC sendsthe STATUS PDU to a transmitting side RLC. To this end, the presentinvention proposes different embodiments depending on how to set ACK_SN.

To achieve the object of the present invention, there is provided amethod for sending status information in mobile telecommunications,including: constructing a status protocol data unit (PDU), the statusPDU being used to provide positive and/or negative acknowledgements ofacknowledged mode data (AMD) PDUs or portions of AMD PDUs (=RLC dataPDUS); and transmitting the constructed status PDU to a peer RLC entity(or lower layer), wherein the constructing step is performed byconsidering available resources such that the constructed status PDUfits to the total size of the available resources.

The constructing step may further include: including NACK elements inincreasing sequence number order; and including information indicatingup to which AMD PDUs the status information is included in the statusPDU.

The information may refer to ACK_SN, the ACK_SN being set to the SN ofthe next not completely received AMD PDU which is not indicated with aNACK_SN in the status PDU.

The NACK elements may be included in increasing sequence number orderfrom the first not received AMD PDU or portions of AMD PDU up to acertain not received AMD PDU such that the constructed status PDU fitsto the total size of the available resources.

The not received AMD PDU or portions of AMD PDUs may not exist betweentwo consecutive not received PDUs.

The not received AMD PDU or portions of AMD PDU may be allowed to existin between two consecutive not received PDUs.

The available resources may refer to the total size of RLC PDUsindicated by lower layer.

The method may further include receiving an indication from a lowerlayer (MAC) about the total size of RLC PDUs.

The constructing step may be performed by including a NACK_SN element ofa first not received AMD PDU or portions of AMD PDUs and optionallyfurther including at least one NACK_SN element of other not received AMDPDUs or portions of AMD PDUs.

The NACK_SN element may include a NACK_SN and optionally a SOstart and aSOend.

If the status PDU is a partial status PDU, an indicator may be used toindicate that the status PDU is the partial status PDU.

In another aspect of the present invention, there is provided a methodfor sending status information in mobile telecommunications, in a methodof delivering status information in which a receiving side radio linkcontrol (RLC) entity reports a data (data protocol units, PDUs) receivedstate to a transmitting side RLC entity, the method including:constructing by the receiving side RLC entity a STATUS PDU includinginformation related to a reception state of RLC data PDUs by consideringan available radio resource; and transmitting by the receiving side RLCentity the constructed STATUS PDU to the transmitting side RLC entity,wherein the constructing step may include: selectively includingincorrectly received NACK_SNs as many as being transmittable by usingthe available radio resource; and setting a value of ACK_SN to a valueof VR(MS).

In one aspect of the present invention, there is provided a receivingside radio link control (RLC) entity in mobile telecommunicationscomprising a module configured to: check a currently available radioresource; construct a STATUS protocol data unit (PDU) by considering theavailable radio resource, wherein negative acknowledgement (NACK)elements are included in the STATUS PDU to be fit to the size of theavailable radio resource and a value of ACK_SN is set; and send theconstructed STATUS PDU to a peer RLC entity.

Advantageous Effect

The related art does not define an operation method in case where anavailable radio resource is smaller in size than a STATUS PDU to be sentby a receiving side AM RLC, which causes RLC protocols to come in adeadlock situation. The present invention proposes a method forconstructing a partial STATUS PDU to allow a transmission of a STATUSPDU even under a situation that a radio resource is not sufficient, soas to enable a stable operation of a protocol regardless of radiocircumstances.

MODE FOR INVENTION

The present invention is applied to a mobile communication system, andparticularly, to an evolved universal mobile telecommunications system(E-UMTS) evolved from the UMTS. However, the present invention may notbe limited to the system, but applicable to any communication system andcommunication protocol complying with the scope of the presentinvention.

As the present features may be embodied in several forms withoutdeparting from the characteristics thereof, it should also be understoodthat the above-described embodiments are not limited by any of thedetails of the foregoing description, unless otherwise specified, butrather should be construed broadly within its scope as defined in theappended claims, and therefore all changes and modifications that fallwithin the metes and bounds of the claims, or equivalents of such metesand bounds are therefore intended to be embraced by the appended claims.

Terms containing ordinal numbers such as 1, 2 and the like, may be usedto describe various components, but the components may not be limited tothe terms. The terms are used for the purpose of distinguishing onecomponent from another component. For example, a first component may benamed as a second component without departing from the scope of thepresent invention, and similarly, the second component may be named asthe first component. A term ‘and/or’ will include a combination ofplural associated items or any of plural associated items.

When mentioning that one component is ‘connected’ or ‘accessed’ toanother component, the one component may be directly connected oraccessed to the another component; however, any intermediatecomponent(s) may exists therebetween. On the other hand, when mentioningthat one component is ‘directly connected’ or ‘directly accessed’ toanother component, it could be understood that other intermediatecomponents do not exist therebetween.

Terms used in the present invention are used to illustrate the preferredembodiments, but not intended to limit the present invention. A singularrepresentation may include a plural representation as far as itrepresents a definitely different meaning from the context. Terms‘include’ or ‘has’ used in the present invention should be understoodthat they are intended to indicate an existence of feature, number,step, operation, component, item or any combination thereof, disclosedin the specification, but should not be understood that they areintended to previously exclude an existence of one or more otherfeatures, numbers, steps, operations, components, or any combinationthereof or possibility of adding those things. As far as not beingdefined differently, all terms used herein including technical orscientific terms may have the same meaning as those generally understoodby an ordinary person skilled in the art to which the present inventionbelongs to. Commonly used terms having the same meanings defined in thedictionary should be construed as having the meanings equal to thecontextual meanings. As far as not being definitely defined in thepresent invention, such terms should not be construed as having ideal orexcessively formal meanings.

Hereinafter, description will be given in detail of the preferredembodiments according to the present invention with reference to theaccompanying drawings. For the sake of brief description with referenceto the drawings, the same or equivalent components regardless ofreference numerals will be provided with the same reference numbers, anddescription thereof will not be repeated.

The present invention allows a transmission of STATUS PDU even when anavailable radio resource is smaller in size than the STATUS PDU in casewhere a receiving side RLC sends the STATUS PDU to a transmitting sideRLC, so as to prevent a deadlock situation of RLC protocols. To thisend, the present invention conceptually defines a new STATUS PDU, andsets ACK_SN according to the construction of the defined STATUS PDU. Forthe sake of explanation, such STATUS PDU is referred to as ‘partialSTATUS PDU’ or ‘short STATUS PDU’. However, the partial STATUS PDUdefined in the present invention may not be a STATUS PDU limited by themeaning of ‘partial’ in a dictionary, but denote that it is smaller thanthe existing STATUS PDU and has a different function. Meanwhile, inorder to distinguish the type of STATUS PDU defined in the presentinvention and the existing STATUS PDU, the existing STATUS PDU may bereferred to as ‘first type of STATUS PDU (or normal STATUS PDU), and theSTATUS PDU defined in the present invention may be referred to as‘second type of STATUS PDU (or partial STATUS PDU).

Also, the present invention assumes that a receiving side RLC is under acircumstance that it cannot send the existing STATUS PDU to atransmitting side RLC using the current radio resource. Thus, thepresent invention proposes, in the preferred embodiments, a method forconstructing (generating) a so-called partial STATUS PDU, such that areceiving side RLC can send a STATUS PDU using an available radioresource, and allow a transmission of the constructed partial STATUS PDUto a transmitting side RLC.

Hereinafter, a format of status PDU defined in the present invention andfields of the status PDU, namely, ACK_SN field, NACK_SN field and thelike, will be described with reference to FIGS. 4 and 5.

FIG. 4 is a format of STATUS PDU currently used in the LTE system. InFIG. 4, a horizontal axis denotes a length of an RLC STATUS PDU with 8bits, namely, 1 octet.

Each field of the RLC STATUS PDU will now be described.

1. Data/Control (D/C) Field: 1 Bit

-   -   This field indicates whether a corresponding RLC PDU is either        RLC data PDU or RLC control PDU.

2. Control PDU Type (CPT) Field: 3 Bits

-   -   This field indicates what type a corresponding control PDU is.        The RLC control PDU currently defines only the STATUS PDU.

3. Acknowledgement Sequence Number (ACK_SN)

-   -   Two types of ACK_SN will be defined as follows.        -   1-1) A type of ACK_SN is an RLC SN of a first PDU whose            information is not included in a STATUS PDU.        -   1-2) Upon receiving the STATUS PDU, a transmitting side            determines that all the PDUs among PDUs up to the PDU with            ACK_SN-1 have successfully been received by a receiving            side, excluding PDUs indicated in the STATUS PDU with            NACK_SN or portions of PDUs indicated in the STATUS PDU with            NACK_SN, SOstart and SOend.

Such ACK_SN was applied to embodiments of FIGS. 6 and 8 according to thepresent invention.

-   -   2-1) Another type of ACK_SN is an RLC SN of a first PDU whose        information is included in a STATUS PDU.    -   2-2) Upon receiving the STATUS PDU, the transmitting side        determines that all the PDUs among PDUs up to the PDU with the        ACK_SN have successfully been by the receiving side, excluding        PDUs indicated in the STATUS PDU with NAC_SN or portions of PDUs        indicated in the STATUS PDU with NACK_SN, SOstart and SOend.

Such ACK_SN was applied to embodiments of FIGS. 7 and 9 according to thepresent invention.

4. Extension 1 (E1): 1 Bit

This indicates whether there is another NACK_SN element following acurrent NACK_SN element (i.e., indicated with NACK_SN or with NACK_SN,SOstart and SOend).

5. NACK_SN (Negative Acknowledgement Sequence Number)

This is an RLC SN of an unsuccessfully received AMD PDU or AMD PDUsegment.

5. Extension 2 (E2); 1 Bit

This indicates whether there are SOstart and SOend fields correspondingto a current NACK_SN.

6. Segment Offset Start (SOstart) and Segment Offset End (SOend)

These are used when only a part (segment) of PDU with NACK_SN is NACK. Afirst byte of the part corresponds to the SOstart and the last bytethereof corresponds to the SOend.

In the meantime, the receiving side AM RLC cannot always trigger aSTATUS PDU, but can trigger a status reporting only when a specificcondition is met. Such condition is referred to as ‘status reportingtrigger’, and the LTE system currently uses two conditions as follows.

The first condition is a polling of a transmitting side.

That is, when desiring to receive a status report from a receiving side,the transmitting side AM RLC sets a poll bit for an RLC data PDU fortransmission. The receiving side AM RLC then triggers the status reportupon receiving the poll bit set RLC data PDU.

The second condition is a detection of an unsuccessful reception of RLCdata PDU.

That is, upon detecting an unsuccessfully received RLC data PDU (i.e.,AMD PDU or AMD PDU segment) after completing a HARQ reordering, thereceiving side AM RLC triggers the status report.

In addition, when the status report is triggered, the receiving side AMRLC sends a reception buffer state to the transmitting side using aSTATUS PDU. Here, the STATUS PDU includes information up to the last PDU(=VR(MS)) among PDUs within the range of a PDU (=VR(R)) with a startpoint of a receiving window to a HARQ reordering completed PDU. Here,the VR(R) and VR(MS) denote state variables, which are managed by thereceiving side AM RLC and used for a receiving window, a status reportand the like. Among others, the receiving AM RLC manages additionalstate variables.

Such additional state variables of the receiving side AM RLC aredescribed as follows.

-   -   VR(R): Receive state variable.        -   It hold a value of a sequence number (SN) of an AMD PDU            subsequent to the last AMD PDU among AMD PDUs received            in-sequence.        -   It is a first AMD PDU among AMD PDUs which are not            completely (successfully) received by the receiving side AM            RLC.        -   It serves as the lower edge of the receiving window.        -   It is initially set to 0. When completely receiving an AMD            PDU with SN=VR(R), it is updated to a value of SN of a first            incompletely received AMD PDU subsequent to the AMD PDU.    -   VR(MR): Maximum acceptable receive state variable.        -   It holds a value of SN of the first AMD PDU among AMD PDUs            outside a receiving window.        -   It serves as the higher edge of the receiving window.        -   It is updated, for example, to VR(MR)=VR(R)+AM_Window_size            when the VR(R) is updated.    -   VR(X): T_reordering state variable        -   It holds a value of SN of an RLC data PDU subsequent to an            RLC data PDU which triggered a T_reordering as a timer for            managing a HARQ reordering.        -   A receiving side AM RLC drives the T_reordering upon            receiving an out-of-sequence RLC data PDU under a condition            that no T_reordering is triggered, and sets the VR(X) to the            value of SN of an RLC data PDU subsequent to the RLC data            PDU.    -   VR(MS): Maximum status transmit state variable        -   This state variable is used for including in a STATUS PDU            information only related to RLC data PDUs for which the HARQ            reordering is completed.        -   It is initially set to 0, and upon completely receiving an            AMD PDU with SN-VR(MS), it is updated to a value of SN of a            first incompletely received AMD PDU following the AMD PDU.    -   Upon the T_reordering expired, it is updated to a value of SN of        a first incompletely received AMD PDU among AMD PDUs higher than        VR(X). ACK_SN is set to the VR(MS) so as to construct a STATUS        PDU.    -   VR(H): highest received state variable        -   It holds a value of the very next SN of the highest SN among            RLC data PDUs received by the receiving side AM RLC, namely,            a value of SN of an RLC data PDU which is first            unsuccessfully received by the receiving side AM RLC.        -   It is initially set to 0, and upon receiving an RLC data PDU            higher than VR(H), it is updated to a value of SN of an RLC            data PDU subsequent to the RLC data PDU.

FIG. 5 illustrates an exemplary construction of a STATUS PDU in the LTEsystem, which illustrates an exemplary status report triggering,considering an HARQ reordering of the LTE system. Here, for the sake ofdescription, an AMD PDU segment is not considered in FIG. 5. Referringto FIG. 5, when t=T1, it is assumed that VR(R)=0, VR(X)=6 and VR(MX)=0.In FIG. 5, data (AMD PDU) received at each time t is shadowed (i.e.,received), and reception failure is data of non-shadowed portions.

t=T0: initial state

-   -   A receiving side AM RLC is in the initial state after the entity        generation.    -   All the state variables have initial values.

t=T1: AMD PDU 5 is received

-   -   Upon receiving the AMD PDU 5 out of sequence, VR(X) is updated        to 6 (i.e., VR(X)=6) and T_reordering is started.    -   Since an AMD PDU 0 has not been received, VR(R)=0 and VR(MS)=0        are maintained.

t-T2: the AMD PDU 0 is received

-   -   Upon receiving the AMD PDU 0 which is AMD PDU with VR(R)=VR(MS),        VR(R) and VR(ms) are all updated to 1, and the AMD PDU 0 is        delivered to an upper layer.    -   VR(X)=6 is maintained and T_reordering is continuously run.

t=T3: AMD PDU 6 is received

-   -   Even if the AMD PDU 6 is received, VR(R), VR(MS) and VR(X) are        under the same states as in t=T2 without a change.

t=T4: AMD PDU 8 is received

-   -   Even if the AMD PDU 8 is received, VR(R), VR(MS) and VR(X) are        under the same states as in t=T3 without a change.

t=T5: T_reordering expires

-   -   When the T_reordering expires, VR(MS) is updated to an AMD PDU        7, which is a first incompletely received AMD PDU among AMD PDUs        higher than VR(X).    -   A STATUS PDU is constructed as shown in FIG. 5 for transmission,        based upon information on PDUs within the range of VR(R)=1 to        VR(MS)=7.    -   T_reordering is restarted when an AMD PDU which is higher than        the updated VR(MS) has been received. Accordingly, VR(X) is        updated to 9 (i.e., VR(X)=9) and T_reordering is restarted.

A transmitting side AM RLC having received the STATUS PDU, as shown inFIG. 5, interprets a reception buffer state as follows.

-   -   Unsuccessfully transmitted AMD PDUs are 1, 2, 3 and 4.    -   Since ACK_SN=7, AMD PDUs 0, 5 and 6, which are not NACK among        AMD PDUs 0 to 6, have successfully been transmitted.    -   VT(A), which is a state variable serving as a start point of a        transmitting window, is updated from 0 to 1. VT(A) holds a SN of        a subsequent AMD PDU for which ACK should first be received in        sequence.

FIG. 6 illustrates a construction of a partial STATUS PDU in accordancewith a first exemplary embodiment of the present invention. Here, thefirst exemplary embodiment of FIG. 6 is described under the assumptionthat data has been received, as shown in FIG. 5, and also a receivingside RLC is able to send two NACK_SN elements to a transmitting side RLCusing a currently available radio resource. That is, like the STATUS PDUshown in FIG. 5, a STATUS PDU to be sent from the receiving side RLC tothe transmitting side RLC matches with an intended STATUS PDU of FIG. 6.However, the receiving side RLC is under the state that it cannot sendsuch STATUS PDU to the transmitting side RLC using the currentlyavailable radio resource. Therefore, a partial STATUS PDU according tothe present invention shown in FIG. 6 is constructed.

The first embodiment of FIG. 6 illustrates that NACK information as muchas being transmittable by an available radio resource, not informationup to VR(MS), is included in a STATUS PDU for transmission. It issummarized as follows; {circle around (1)} NACK_SNs are included as manyas being transmittable by an in-sequence given radio resource, and{circle around (2)} ACK_SN is not necessarily set to VR(MS), but set toa random value capable of including the NACK_SNs within the range ofVR(R)≦SN≦VR(MS). For example, if the first embodiment of FIG. 6 isapplied to the STATUS PDU of FIG. 5, as the random values, only twoNACK_SN elements (i.e., NACK_SN1 and NACK_SN2) can sequentially beincluded in the partial STATUS PDU, as shown in FIG. 6.

Hereinafter, an operation performed between the transmitting side AM RLCand receiving side AM RLC will be described in more detail withreference to the first embodiment of FIG. 6.

1. When a receiving side AM RLC constructs STATUS PDU,

-   -   1-1) the receiving side AM RLC considers an included NACK_SN        list, to set ACN_SN to a random value within the range of        VR(R)≦SN≦VR(MS), such that the total size of the STATUS PDU        cannot be greater than a given radio resource. The newly set        ACK_SN value may depend on a capability of a currently available        radio resource of the receiving side RLC. In more detail, the        ACK_SN is set to one (e.g., set to ACK_SN=3 of FIG. 6) within        the range of (the last NACK_SN included in the STATUS PDU,        namely, NACK_SN2 of FIG. 6)≦SN≦(the first NACK_SN not included        in the STATUS PDU, namely, NACK_SN3 of FIG. 6). Accordingly,        NACK_SNs to be desirably included can be included in the partial        STATUSPDU.    -   1-2) NACK_SN1 as the first NACK_SN is set to VR(R).    -   1-3) SNs of all the unsuccessfully received PDUs, among PDUs        within the range of NACK_SN1≦SN≦ACK_SN, are set to NACK_SN        elements in an increasing SN order (i.e., NACK_SN1 and NACK_SN2        of FIG. 6).

2. When the transmitting side AM RLC receives the partial STATUS PDU,

-   -   2-1) the transmitting side AM RLC determines that PDUs within        the range of VT(A)≦SN<NACK_SN1 have successfully been sent.    -   2-2) PDUs with NACK_SN, among PDUs within the range of        NACK_SN1≦SN<ACK_SN, are determined to be unsuccessfully sent.    -   2-3) PDUs not with NACK_SN, among PDUs within the range of        NACK_SN1≦SN<ACK_SN, are determined to be successfully sent.    -   2-4) VT(A) is set to NACK_SN1.

The first embodiment of FIG. 6 illustrates a method of sequentiallyincluding NACK_SN elements in a STATUS PDU as much as being loadable fortransmission. That is, as shown in FIG. 6, among four unsuccessfullyreceived NACK_SN elements (i.e., NACK_SN1 to NACK_SN4), two NACK_SNelements (i.e., NACK_SN1 and NACK_SN2) are sequentially sent by using acurrently available radio resource. The first embodiment of FIG. 6 isadvantageous in that even if the receiving side does not inform all theinformation required by the transmitting side, maximum statusinformation to be fit to a current radio resource circumstance can besent. The transmitting side and the receiving side perform the same RLCoperations as the related art excluding the difference that ACK_SN isset to a random value other than VR(MS).

In the meantime, the NACK_SN element in the description may actually beNACK_SN itself, or be a set including NACK_SN, SOstart and SOendconsidering segments.

FIG. 7 illustrates another exemplary construction of the partial STATUSPDU in accordance with the first embodiment of the present invention,which illustrates that status PDUs are sent from a receiving side RLCentity to a transmitting side RLC entity using first and second STATUSPDUs, considering an available radio resource.

However, a value of ACK_SN of FIG. 7 is different from that defined inFIG. 6.

That is, explaining the ACK_SN of FIG. 7, an ACK_SN field indicates anRLC SN of a first PDU whose information is included in STATUS PDU. Thatis, when receiving the STATUS PDU, the transmitting side interprets thatall AMD PDUs up to and including the AMD PDU with SN=ACK_SN have beenreceived by its peer AM RLC entity, excluding those AMD PDUs indicatedin the STATUS PDU with NACK_SN and portions of AMD PDUs indicated in theSTATUS PDU with NACK_SN, SOstart and SOend.

ACK_SN may not be set to the same value to that of VR(MS) (i.e.,VR(MS)=11). The ACK_SN is set to 7 (ACK_SN=7) (i.e., the next value ofNACK_SN3=6) for a first STATUS PDU. The first STATUS PDU includes three(indicating the size of a currently available radio resource) ofunsuccessfully received AMD PDUs (i.e., SN=3, 5 and 6), namely,NACK_SN1=3, NACK_SN2=5 and NACK_SN3=6. The ACK_SN is set to 9 (i.e., thenext value of NACK_SN4=8) for a second STATUS PDU. The second STATUS PDUincludes four (indicating the size of a currently available radioresource) of unsuccessfully received AMD PDUs (i.e., SN=3, 5, 6 and 8),namely, NACK_SN1=3, NACK_SN2=5, NACK_SN3=6 and NACK_SN4=8. Inparticular, comparing the embodiments of FIGS. 6 and 7, the transmittingside determines in the embodiment of FIG. 7 that the receiving side hascorrectly received PDUs up to the PDU with ACK_SN, whereas thetransmitting side determines in the embodiment of FIG. 6 that thereceiving side has correctly received PDUs up to the PDU with ACK_SN−1.

FIG. 8 illustrates a construction of a STATUS PDU in accordance with asecond embodiment of the present invention, which illustrates how toconstruct a partial STATUS PDU without including part of NACK_SNelements. Here, the second embodiment of FIG. 8 is under the assumptionthat data has been received as shown in FIG. 5, and also a receivingside RLC can send two NACK_SN elements to a transmitting side RLC byusing a currently available radio resource. That is, like the STATUS PDUof FIG. 5, a STATUS PDU which the receiving side RLC is to send to thetransmitting side RLC is the same as an intended STATUS PDU of FIG. 8.However, the receiving side RLC is under the circumstance that it cannotsend the entire STATUS PDU to the transmitting side RLC using thecurrently available radio resource. Hence, the partial STATUS PDU ofFIG. 8 according to the present invention is constructed. Hereinafter,an exemplary operation between the transmitting side AM RLC and thereceiving side AM RLC will be described with reference to FIG. 8. Thesecond embodiment of FIG. 8 illustrates how to construct a STATUS PDUwithout including portions of NACK_SN elements (e.g., indicated withNACK_SN or with NACK_SN, SOstart and SOend) in order to fit the size ofthe STATUS PDU to an available radio resource. Here, the ACK_SN may beset to VR(MS) as done in the related art. The STATUS PDU shown in FIG. 8may be constructed when only two NACK_SN elements can be included in theSTATUS PDU because an available radio resource is not sufficient in theembodiment of FIG. 6.

The operation between the transmitting side AM RLC and the receivingside AM RLC in the second embodiment of the present invention isdescribed as to follows:

1. When the receiving side AM RLC constructs a STATUS PDU,

-   -   1-1) ACK_SN is set to VR(MS).    -   1-2) NACK_SN1 as a first NACK_SN is set to VR(R).    -   1-3) Some of SNs of unsuccessfully received PDUs are selected        among PDUs within the range of NACK_SN1<SN<ACK_SN to be fit into        a given radio resource, so as to construct a NACK_SN list. It is        assumed in FIG. 7 that two NACK_SN elements can be sent by using        the available radio resource, and thus NACK_SN2=3 is selected.

2. When the transmitting side AM RLC receives the STATUS PDU,

-   -   2-1) PDUs within the range of VT(A)≦SN<NACK_SN1 are determined        to be successfully sent.    -   2-2) PDUs with NACK_SN among PDUs within the range of        NACK_SN1≦SN<ACK_SN are determined to be unsuccessfully sent.    -   2-3) PDUs not with NACK_SN among PDUs within the range of        NACK_SN1≦SN<ACK_SN are determined to be unknown as to whether or        not they are correctly sent.    -   2-4) VT(A) is set to NACK_SN1.

The second embodiment according to the present invention is implementedin order for a receiving side to inform the transmitting side of up towhich PDU it has actually received, by setting ACK_SN to VR(MS) (i.e.,ACK_SN=7 in FIG. 8) as shown in the related art. Also, the NACK_SN listis constructed by selecting some of PDUs with NACK_SN. Accordingly, inorder to avoid a wrong determination of the transmitting side, thereceiving side always sets NACK_SN1 to VR(R) upon the construction ofthe STATUS PDU, and the transmitting side determines to be unknown, notACK, as to whether PDUs not with NACK_SN have successfully been sent.

Here, since the transmitting side determines that PDUs within the rangeof VT(A)≦SN<NACK_SN1 have correctly been sent, if the NACK_SN1 is set toa value greater than the VR(R), a start point of a transmitting windowmoves to an SN greater than SN of an unsuccessfully sent PDU such thatthe transmitting side does not retransmit the unsuccessfully sent PDU.Hence, the NACK_SN1 is set to VR(R).

In addition, in order to avoid the determination that NACK_SNs notincluded in the NACK_SN list are ACK because an available radio resourceis not sufficient, the transmitting side does not determine that whetherthe PDUs not with NACK_SN are ACK among PDUs within the range ofNACK_SN1≦SN<ACK_SN is successfully sent. In the description, the NACK_SNelement may actually be NACK_SN itself. Alternatively, the NACK_SNelement may be a set including NACK_SN, SOstart and SOend.

FIG. 9 illustrates another exemplary construction of the partial STATUSPDU in accordance with the second embodiment of the present invention,which illustrates that a receiving side RLC entity sends status PDUs toa transmitting side RLC entity using first and second STATUS PDUs byconsidering an available radio resource. Here, in this construction, avalue of ACK_SN in FIG. 9 is different from that defined in FIG. 8. TheACK_SN of FIG. 9 is the same as that described in FIG. 7. Referring toFIG. 9, a value of VR(MS) (i.e., VR(MS)=11) is set to a value of ACK_SN(i.e., ACK_SN=11), and the first STATUS PDU includes three (indicatingthe size of a currently available radio resource) of unsuccessfullyreceived AMD PDUs (i.e., SN=3, 5 and 6), namely, NACK_SN1=3, NACK_SN2=5and NACK_SN3=6. The second STATUS PDU includes two (indicating the sizeof a currently available radio resource) of unsuccessfully received AMDPDUs (i.e., SN=8 and 10), namely, NACK_SN1=8 and NACK_SN2=10. Inparticular, comparing the embodiments of FIGS. 9 and 8, the transmittingside determines in FIG. 9 that the receiving side has correctly receivedup to a PDU with ACK_SN, whereas the transmitting side determines inFIG. 8 that the receiving side has correctly received up to a PDU withACK_SN−1.

A third embodiment according to the present invention illustrates thatnormal STATUS PDU and partial STATUS PDU are distinguished by a controlPDU type (CPT) field for transmission. Here, ‘normal’ of the normalSTATUS PDU is not limited to the meaning in the dictionary but is a termused to distinguish the normal STATUS PDU from the partial STATUS PDUdefined in the present invention.

3-bit CPT field exists in a header of an RLC control PDU, so as toinform the type of the corresponding control PDU. However, only one typeof STATUS PDU has been defined so far. Therefore, only CPT=000 is usedand the other values are not used. That is, the third embodimentaccording to the present invention can use the CPT field to indicate thenormal STATUS PDU for CPT=000 and to indicate the partial STATUS PDU forCPT=001, for example.

The third embodiment according to the present invention illustrates thata partial STATUS PDU is added as a type of control PDU and a CPT fieldis used to identify it. That is, when a radio resource is sufficient,the existing normal STATUS PDU is sent, and when the size of radioresource is smaller than the normal STATUS PDU, the partial STATUS PDUis send. Upon receiving a control PDU, the transmitting side uses theCPT field to identify whether the received control PDU is the normalSTATUS PDU or the partial STATUS PDU, and operates accordingly.

On the other hand, in case where the transmitting side is a network, itis important to identify whether a received STATUS PDU is normal STATUSPDU or partial STATUS PDU because the network manages the allocation ofradio resources to a terminal. That is, upon receiving the partialSTATUS PDU from the terminal, the network determines that the terminalhas insufficient radio resources allocated. Accordingly, the network mayallocate more radio resources to the terminal in the next allocation, soas to enable an effective operation.

In the meantime, the third embodiment using the CPT field can be appliedto the first and second embodiments of the present invention. That is,when the CPT field of the third embodiment is used for the partialSTATUS PDU of the first embodiment, a transmitting side having receivedthe partial STATUS PDU including the CPT field (e.g., for CPT=001)determines (analyzes) that a receiving side has not included all theNACK_SNs (i.e., PDUs unsuccessfully received by the receiving side) inthe partial STATUS PDU due to the insufficient radio resources. Hence,the transmitting side can effectively deal with the case ofretransmitting unsuccessfully sent PDUs.

Also, when the CPT field of the third embodiment is used for the partialSTATUS PDU of the second embodiment, the transmitting side alsodetermines (analyzes) based upon the set value of the CPT field that thereceiving side has not included all the NACK_SNs (i.e., PDUsunsuccessfully received by the receiving side) in the partial STATUSPDU. In particular, in this case, the transmitting side determines to beunknown as to whether PDUs not with NACK_SN are successfully sent, andshould continuously store the corresponding PDUs in its buffer.

A receiver according to the present invention may include a module forconstructing a STATUS PDU described in the first and second embodimentsof the present invention.

The module according to the present invention may check a currentlyavailable radio resource and construct the STATUS PDU by considering anavailable radio resource. The module includes NACK elements in theSTATUS PDU to be fit to the available radio resource, and sets a valueof ACK_SN. Here, the module may perform the setting operation as shownin the first and second embodiments upon setting the ACK_SN.

The module then sends the STATUS PDU constructed to be fit to theavailable radio resource to its peer RLC entity.

The receiver according to the present invention basically includes, inaddition to the aforesaid component, software and hardware required forimplementing the scope of the present invention, for example, an outputdevice (e.g., display, speaker and the like), an input device (e.g.,keypad, microphone and the like), a memory, a transceiver (e.g., RFmodule, antenna and the like). Such components can be obviouslyunderstood by those skilled in the art, and thus a detailed descriptionthereof will not be repeated.

Meanwhile, the method according to the present invention, as describedso far, can be implemented by hardware or software, or any combinationthereof. For example, the method according to the present invention maybe stored in a storage medium (e.g., an internal memory of a mobileterminal, a flash memory, a hard disc, etc.). Alternatively, the methodaccording to the present invention can be implemented as codes orcommand words within a software program capable of being executed by aprocessor (e.g., a microprocessor in a mobile terminal).

The present invention has been explained with reference to theembodiments which are merely exemplary. It will be apparent to thoseskilled in the art that various modifications and equivalent otherembodiments can be made in the present invention without departing fromthe spirit or scope of the invention. Also, it will be understood thatthe present invention can be implemented by selectively combining theaforementioned embodiment(s) entirely or partially. Thus, it is intendedthat the present invention cover modifications and variations of thisinvention provided they come within the scope of the appended claims andtheir equivalents.

DESCRIPTION OF DRAWINGS

FIG. 1 is a network architecture of a long term a long term evolution(LTE) system which is the related art mobile communication system;

FIG. 2 is an architecture of a radio interface protocol control planebetween a terminal and an E-UTRAN based upon the 3GPP radio accessnetwork standard;

FIG. 3 is an architecture of a radio interface protocol user planebetween a terminal and an E-UTRAN based upon the 3GPP radio accessnetwork standard;

FIG. 4 is a format of STATUS PDU currently used in the LTE system;

FIG. 5 illustrates an exemplary construction of STATUS PDU in the LTEsystem;

FIG. 6 illustrates a construction of a partial STATUS PDU in accordancewith a first exemplary embodiment of the present invention;

FIG. 7 illustrates another exemplary construction of a partial STATUSPDU in accordance with the first embodiment of the present invention;

FIG. 8 illustrates a construction of STATUS PDU in accordance with asecond embodiment of the present invention; and

FIG. 9 illustrates another exemplary construction of partial STATUS PDUin accordance with a second embodiment of the present invention.

1. A method for sending status information in a mobile communicationssystem, comprising: constructing a status protocol data unit (PDU), thestatus PDU used to provide at least one of a positive acknowledgementand a negative acknowledgement of radio link control (RLC) data PDUs,wherein the RLC data PDUs comprise at least one of acknowledged modedata (AMD) PDUs and portions of AMD PDUs; and transmitting theconstructed status PDU to a peer RLC entity, wherein the constructingstep is performed by considering available resources such that theconstructed status PDU fits to a total size of the available resources,and by using a receive state variable and a maximum status transmitstate variable, and wherein the status PDU is for AMD PDUs with sequencenumbers that include a sequence number of the receive state variable andat least one sequence number between the sequence number of the receivestate variable and a sequence number of the maximum status transmitstate variable.
 2. The method of claim 1, wherein the constructing stepfurther comprises: including negative acknowledgement (NACK) elements inincreasing sequence number order; and including information indicatingup to which AMD PDUs the status information is included in the statusPDU.
 3. The method of claim 2, wherein the information refers to anacknowledgement sequence number (ACK_SN), the ACK_SN being set to asequence number of the next not completely received AMD PDU which is notindicated with a negative acknowledgement sequence number (NACK_SN) inthe status PDU.
 4. The method of claim 2, wherein the NACK elements areincluded in increasing sequence number order from the first not receivedAMD PDU or portions of AMD PDU up to a certain not received AMD PDU suchthat the constructed status PDU fits to the total size of the availableresources.
 5. The method of claim 4, wherein the first not received AMDPDU or portions of AMD PDUs do not exist between two consecutive notreceived PDUs.
 6. The method of claim 4, wherein the first not receivedAMD PDU or portions of AMD PDU are allowed to exist in between twoconsecutive not received PDUs.
 7. The method of claim 1, wherein theavailable resources refers to the total size of RLC PDUs indicated by alower layer.
 8. The method of claim 1, further comprising: receiving anindication from a lower layer about the total size of RLC PDUs.
 9. Themethod of claim 1, wherein the constructing step is performed byincluding a negative acknowledgement (NACK) element of a first notreceived AMD PDU or portions of AMD PDUs and optionally furtherincluding at least one NACK element of other not received AMD PDUs orportions of AMD PDUs.
 10. The method of claim 9, wherein the NACKelement comprises a negative acknowledgement sequence number (NACK_SN)and optionally a segment offset start (SOstart) and a segment offset end(SOend).
 11. The method of claim 1, wherein if the status PDU is apartial status PDU, an indicator is used to indicate that the status PDUis the partial status PDU.
 12. A method for sending status informationfrom a receiving side radio link control (RLC) entity to a transmittingside RLC entity in a mobile communications system, the methodcomprising: constructing by the receiving side RLC entity a statusprotocol data unit (STATUS PDU) by considering an available radioresource such that the constructed STATUS PDU fits to a total size ofthe available radio resource, the STATUS PDU including informationrelated to a reception state of RLC data PDUs; and transmitting by thereceiving side RLC entity the constructed STATUS PDU to the transmittingside RLC entity, wherein the constructing step comprises: selectivelyincluding negative acknowledgement sequence numbers (NACK_SNs) as manyas being transmittable by using the available radio resource, and byusing a receive state variable and a maximum status transmit statevariable; and setting an acknowledgement sequence number (ACK_SN) valueto a sequence number value of the maximum status transmit statevariable, wherein the status PDU is for AMD PDUs with sequence numbers,that include a sequence number of the receive state variable and atleast one sequence number between the sequence number of the receivestate variable and a sequence number of the maximum status transmitstate variable.
 13. A receiving side radio link control (RLC) entity ina mobile communications system, comprising a module configured to: checkan available radio resource; construct a status protocol data unit(STATUS PDU) by considering the available radio resource so that theSTATUS PDU fits to a total size of the available radio resource, and byusing a receive state variable and a maximum status transmit statevariable, wherein negative acknowledgement (NACK) elements are includedin the STATUS PDU, and an acknowledgement sequence number (ACK_SN) valueis set; and send the constructed STATUS PDU to a peer RLC entity,wherein the status PDU is for AMD PDUs with sequence numbers thatinclude a sequence number of the receive state variable and at least onesequence number between the sequence number of the receive statevariable and a sequence number of the maximum status transmit statevariable.